Nucleating activity

Recent studies have further examined the iron stress response of pseudomonads using an iron-regulated, ice-nucleation gene reporter (inaZ) for induction of the iron stress response (17,18,84). This particular reporter system was developed by Loper and Lindow (85) for study of microbial iron stress on plant surfaces but was later employed in soil assays. In initial. studies, cells of Pseudomonas fluorescens and P. syringae that contained the pvd-inaZ fusion were shown to express iron-responsive ice-nucleation activity in the bean rhizosphere and phyllosphere. Addition of iron to leaves or soil reduced the apparent transcription of the pvd-inaZ reporter gene, as shown by a reduction in the number of ice nuclei produced. 

The interphases between MDs should not be able to cause nucleation of the semicrystalline phase. If the interphase displays nucleation activity, first-order crystallization kinetics may be obtained however, the supercooling at which dynamic crystallization from the melt occurs will not be the maximum that could be possibly attained if homogeneous nucleation were in place. 

The rate of dispersion (co)polymerization of PEO macromonomers passes through a maximum at a certain conversion. No constant rate interval was observed and it was attributed to the decreasing monomer concentration. At the beginning of polymerization, the abrupt increase in the rate was attributed to a certain compartmentalization of reaction loci, the diffusion controlled termination, gel effect, and pseudo-bulk kinetics. A dispersion copolymerization of PEO macromonomers in polar media is used to prepare monodisperse polymer particles in micron and submicron range as a result of the very short nucleation period, the high nucleation activity of macromonomer or its graft copolymer formed, and the location of surface active group of stabilizer at the particle surface (chemically bound at the particle surface). Under such conditions a small amount of stabilizer promotes the formation of stable and monodisperse polymer particles. 

Popov, A. V., Severin, F., and Karsenti, E. (2002). XMAP215 is required for the microtubule-nucleating activity of centrosomes. Curr. Biol. 12, 1326-1330. 

The aim of this section, therefore, is to correlate systematically the compatibilization of PPE/SAN 60/40 blends by SBM triblock terpolymers with the foaming behavior of the resulting blend. The reduction of the blend phase size, the improved phase adhesion, a potentially higher nucleation activity of the nanostructured interfaces, and the possibility to adjust the glass transitional behavior between PPE and SAN, they all promise to enhance the foam processing of PPE/SAN blends. 

It appears that both compatibilization and the nanostructure formation at the interface play a key role for nucleation. The supposed heterogeneous nucleation activity will therefore be discussed in more detail. Heterogeneous nucleation in general is strongly affected by the particle size and the interfacial properties [79, 80], As the particle size of the PPE phase is well above the critical radius of nucleation of several nanometers [80], the interface demands closer examination. 

In summary, compatibilization of PPE/SAN blends via SBM triblock terpolymers allows one to enhance significantly the homogeneity of the foam, while simultaneously reducing the cell size by heterogeneous nucleation activity of the... 

The studies of Facchini et al. (2000), Gysel et al. (2004), Kiss et al. (2005) and Dinar et al. (2006) highlight the importance of organic aerosol components in the cloud-nucleating activities of atmospheric particles. However, a question still remains to be answered What is the truly effect of organic components on aerosol CCN activity Furthermore, does the WSOM enhance cloud droplet activation or, on the other hand, delay droplet activation ... 

Duman, 2001 Duman et al., 1993 Wu and Duman, 1991). When its ice-nucleating activity is inhibited, the THP-activator protein does not jeopardize the deep supercooling that may be critical for survival of D. canadensis during periods of extreme cold. 

Lee, R.E. Jr., M.R. Lee, and J.M. Strong-Gunderson (1993a). Insect cold-hardiness and ice nucleating active microorganisms including their potential use for biological control. J. Insect. Physiol. 39 1-12. 

Certain strains of bacteria can competitively exclude other strains. Lindow (117) found that Ice (ice nucleation-active) populations of Pseudomonas syringae on corn plants Zea mays L.) were reduced by prior colonization of the leaves by Ice strains (ice nuleation-deficient). Interestingly, the total bacterial population was not affected by the prior inoculation of Ice strains (117). For these reasons, Lindow (117) concluded that the antagonism between these strains resulted from competitive exclusion of new arrivals to an occupied niche rather than competitive displacement. As the carrying capacity of leaf surfaces for bacteria is low relative to other plant habitats, particularly roots (101), preemptive colonization by one strain may be sufficient to reduce the population size of similar strains. The importance of competition for space among naturally colonizing microbes remains unknown. 

This order is indicative of the relative magnitudes of the nucleation activation energies that control the different nucleation mechanisms. 

Cell Biol. 28, 1185-1189, 1996 Szymanski, P.T., Calponin (CaP) as a latch-bridge protein — a new concept in regulation of contractility in smooth muscle, J. Muscle Res. Cell Motil. 25,7-19,2004 Lehman, W., Craig, R., Kendrick-Jones, J., and Sulherland-Smith, A.J., An open or closed case for the conformation of calponin homology domains on F-actin J. Muscle Res. Cell Motil. 25, 351-358, 2004 Feijani, L, Fattoum, A., Maciver, S.K. et al., A direct interaction with calponin inhibits the actin-nucleating activity of gelsohn, Biochem. J. 396, 461 68, 2006. 

Figure 1. Models of coronin function. A) Speculative model of coronin function (1995, E. L. de Hostos, unpublished) suggesting the involvement of coronin in actin dynamics in partnership with other actin-binding proteins. B) Current model of core coronin functions. " 1) Coronin recruits Arp2/3 complex to existing actin filaments and promotes the formation of branches. 2) Coronin stimulates the activity of cofilin to depolymerize actin filaments at their pointed (ADP-actin containing ends) directly, or by recruiting the SSH1L phosphatase. 3) In the absence of F-actin, coronin inhibits the nucleation activity of Arp2/3.

Bruce Goode and coworkers started to reveal the nature of this partnership when they found that Cm Ip bound Arp2/3 via its coiled-coil and recruited it to the sides of pre-existing F-actin filaments. In the absence of pre-existir filaments they found, however, that Crnlp inhibited the actin-nucleating activity of the complex. Therefore, they proposed that coronin inhibits Arp2/3-mediated polymerization in the cytoplasm, but promotes nucleation and branching at the cell cortex. ... 

Fig. 1. Toxin-catalyzed ADP-ribosylation inhibits nucleation activity of the gelsolin-octin complex. In the presence of Ca, gelsotin forms a 1 1 and a 1 2 complex with octin monomers at the so-called EGTA-resistant (a) and Ca -sensitive (b) binding site, respectively. Gelsolin-actin complexes act as nuclei for actin polymerization. Actin bound to both sites (a, b) can be ADP-ribosylated. Whereas ADP-ribosylation of actin bound to the EGTA-resistant site has no effect on nucleation, ADP-ribosylation of actin bound to the Ca " -sensitive site inhibits nucleation activity of the gelsolin-actin complex...

Glass beads PET Epoxy APES silane increases interfacial adhesion but hinders crystallization of PET by reducing nucleating activity of filler fracture resistance increased but no improvement of HjO resistance 23 33... 

Basicly, the effects are caused by the nucleating activity of different inhomogeneities. They can become more complicated if the second component, in particular their just created crystals, acts as a crystallization nucleating inhomogeneity. Such a - in some cases mutual - nucleating activity is hidden under usual conditions. Finally, some blends, e.g. that of PBTP and PVDF, exhibit a most complicated mutual nucleation behaviour the molten first component acts as nucleating substrate for the second one and becomes then itself nucleated by the newly created crystals of that component. 

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